This invention relates to a valve bonnet structure. Particularly, to a bonnet lock assembly installed about the valve bonnet for locking the valve bonnet to the valve body.
Valve bonnets are well known in the prior art. Typically, a valve bonnet is threadably mounted to a valve body. The bonnet carries a valve stem having a valve member at its distal end for engagement with a valve seat formed in the valve body. The bonnet is threaded to the valve body primarily to establish a seal between the bonnet and the valve body. The bonnet also aids in properly positioning the valve stem relative to the valve seat. Therefore, once threaded to the proper torque, further rotation of the bonnet relative to the valve body is undesirable. Consequently, various locking arrangements about the bonnet have been attempted in the prior art. A typical arrangement involves the placement of a roll pin installed in the valve body adjacent to the bonnet to prevent accidental removal of the bonnet. In such an arrangement, the roll pin allows some rotation of the bonnet. In addition, relatively low torque may bend the roll pin, thereby reducing its effectiveness in preventing accidental removal of the valve bonnet.
Attempts have been made to overcome the disadvantages associated with the typical roll pin retaining arrangement. In U.S. Pat. No. 4,118,007, a valve structure is disclosed which includes a radially enlarged recess for receiving a bonnet. A retainer pin is received in a hole provided in the body of the valve radially outwardly of the recess. A semicircular notch formed in the valve body extends about the pin hole and provides a support shoulder for the pin to aid in preventing outward deformation of the pin upon rotation of the bonnet.
U.S. Pat. No. 3,049,332 and related U.S. Pat No. 3,153,421, show a locking member comprising a retainer element which slips over the valve bonnet to secure it from rotation. The retainer element is secured against rotation by a lock screw threaded into the valve body.
The invention of the present disclosure provides an improved bonnet lock assembly to overcome the disadvantages associated with retainer elements presently available to prevent undesirable rotation of a valve bonnet.